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Title: Chemisorption-induced n-doping of MoS{sub 2} by oxygen

Both chemisorption and physisorption affect the electronic properties of two-dimensional materials, such as MoS{sub 2}, but it remains a challenge to probe their respective roles experimentally. Through repeated in-situ electrical measurements of few-layer MoS{sub 2} field-effect transistors in an ultrahigh vacuum system with well-controlled oxygen partial pressure (6 × 10{sup −8} mbar–3 × 10{sup −7} mbar), we were able to study the effect of chemisorption on surface defects separately from physically adsorbed oxygen molecules. It is found that chemisorption of oxygen results in n-doping in the channel but negligible effect on mobility and on/off ratio of the MoS{sub 2} transistors. These results are in disagreement with the previous reports on p-doping and degradation of the device's performance when both chemisorption and physisorption are present. Through the analysis of adsorption-desorption kinetics and the first-principles calculations of electronic properties, we show that the experimentally observed n-doping effect originates from dissociative adsorption of oxygen at the surface defects of MoS{sub 2}, which lowers the conduction band edge locally and makes the MoS{sub 2} channel more n-type-like as compared to the as-fabricated devices.
Authors:
; ;  [1] ;  [2]
  1. Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, Singapore 117583 (Singapore)
  2. Engineering Science Program, Faculty of Engineering, National University of Singapore, Singapore, Singapore 117579 (Singapore)
Publication Date:
OSTI Identifier:
22489440
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 108; Journal Issue: 6; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ADSORPTION; CHEMISORPTION; DESORPTION; FIELD EFFECT TRANSISTORS; LAYERS; MOLECULES; MOLYBDENUM SULFIDES; OXYGEN; PARTIAL PRESSURE; PERFORMANCE; SURFACES; TWO-DIMENSIONAL SYSTEMS